To study the abundance of each bacterial group within the whole wetland we estimated the total concentration of their biomass. The actual biomass was obtained by integrating their concentration within the simulated longitudinal section (obtaining kgCOD m− 1) and multiplying it by the width of the wetland (5.3 m) (obtaining kgCOD). Biomass was later normalised to a cubic meter of granular material by dividing it by the volume of the entire wetland.